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Jul 3, 2011

Can Solar Power be Harnessed in Low Earth Orbit

The following article from this weeks Economist excites us. We are all too often overwhelmed by the earthly press of Fox, MSNBC, and the like who do nothing but tear each other and humanity down. The article below speaks of the best of mankind. The collective genius of multiple cultures and people working on a way to bring the benefits of science to the masses. The success of a low earth electric generating station is perhaps far fetched and may not happen in our lifetimes but the science learned from attempting it may make current technologies easier to produce and perfect.

We encourage you all to read the Economist Science and Technology section on the web each week for great articles like this it will democratize you in a way that Fox and MSNBC will not

THE idea of collecting solar energy in space and beaming it to Earth has been around for at least 70 years.In “Reason”, a short story by Isaac Asimov that was published in 1941, a space station transmits energy collected from the sun to various planets using microwave beams.

The advantage of intercepting sunlight in space, instead of letting it find its own way through the atmosphere, is that so much gets absorbed by the air. By converting it to the right frequency first (one of the so-called windows in the atmosphere, in which little energy is absorbed) a space-based collector could, enthusiasts claim, yield on average five times as much power as one located on the ground.

The disadvantage is cost. Launching and maintaining suitable satellites would be ludicrously expensive. But perhaps not, if the satellites were small and the customers specialised. Military expeditions, rescuers in disaster zones, remote desalination plants and scientific-research bases might be willing to pay for such power from the sky. And a research group based at the University of Surrey, in England, hopes that in a few years it will be possible to offer it to them.

Heavenly powerThis summer, Stephen Sweeney and his colleagues will test a laser that would do the job which Asimov assigned to microwaves. Certainly, microwaves would work: a test carried out in 2008 transmitted useful amounts of microwave energy between two Hawaiian islands 148km (92 miles) apart, so penetrating the 100km of the atmosphere would be a doddle. But microwaves spread out as they propagate. A collector on Earth that was picking up power from a geostationary satellite orbiting at an altitude of 35,800km would need to be spread over hundreds of square metres. Using a laser means the collector need be only tens of square metres in area.

Dr Sweeney’s team, working in collaboration with Astrium, a satellite-and-space company that is part of EADS, a European aerospace group, will test the system in a large aircraft hangar in Germany. The beam itself will be produced by a device called a fibre laser. This generates the coherent light of a laser beam in the core of a long, thin optical fibre. That means the beam produced is of higher quality than other lasers, is extremely straight (even by the exacting standards of a normal laser beam) and can thus be focused onto a small area. Another bonus is that such lasers are becoming more efficient and ever more powerful.

In the case of Dr Sweeney’s fibre laser, the beam will have a wavelength of 1.5 microns, making it part of the infra-red spectrum. This wavelength corresponds to one of the best windows in the atmosphere. The beam will be aimed at a collector on the other side of the hangar, rather than several kilometres away. The idea is to test the effects on the atmospheric window of various pollutants, and also of water vapour, by releasing them into the building.

Assuming all goes well, the next step will be to test the system in space. That could happen about five years from now, perhaps using a laser on the International Space Station to transmit solar power collected by its panels to Earth. Such an experimental system would deliver but a kilowatt of power, as a test. In 10-15 years Astrium hopes it will be possible to deploy a complete, small-scale orbiting power station producing significantly more than that from its own solar cells.

Other researchers, in America and Japan, are also looking at using lasers rather than microwaves to transmit power through the atmosphere. NASA, America’s space agency, has started using them to beam energy to remotely controlled drones. Each stage of converting and transmitting power results in a loss of efficiency, but with technological improvements these losses are being reduced. Some of the latest solar cells, for instance, can covert sunlight into electricity with an efficiency of more than 40%.

In the 1980s, 20% was thought good.

Whether the Astrium system will remain a specialised novelty or will be the forerunner of something more like the cosmic power stations of Asimov’s imagination is anybody’s guess. But if it comes to pass at all, it will be an intriguing example, like the geostationary communications satellites dreamed up by Asimov’s contemporary, Arthur C. Clarke, of the musings of a science-fiction author becoming science fact.

1 comment:

The really big benefits of space solar will happen when space launch costs come down. This is starting to happen now as private companies that are interested in reducing the cost of access to space are building their own rockets. Currently all rockets are expendable or cost about 80% of the cost of a new rocket (specifically the shuttle's solid boosters which also emit a fair amount of air pollution). Many rockets now emit WATER when they burn clean hydrogen fuel.

Work is underway to create re-usable rockets that will bring space access costs down closer to that of air freight. We expect launch costs to drop as much as a factor of 10 in a few years and to continue to drop.

The enormous mass of equipment that would be required to supply even current global energy demands of about 17,000 Gigawatts equivalent would require covering so much land with giant solar collector and wind farms that it would strain the economies of every nation. On the other hand, space solar uses about 1000 times less massive solar arrays since they are in space and do not have to resist gravity, wind, hail, rust, dust, corrosion and vandalism.

While some are concerned about how to get the power to the ground, lots of people do not like power lines either. Take your pick! Whichever system is used would have multiple safely interlocks to prevent any problems. Power transmission in tight beams can be very efficient, and comparable to transmission lines.

Space Solar should become a major component in supplying the world with clean electricity and eventually, even with clean synthetic fuels created with that electricity.A large amount of information about space solar is at: http://www.nss.org/settlement/ssp/